How do I restore the original window configuration?
In 'User Preferences' under the 'File' tab, you can uncheck the 'Load UI' option.

Save User Preferences.

Then restart Blender.

This will cause blender to load the default window layout.

If you want to keep a window layout, you need to remember to re-check 'Load UI' once blender has restarted.



To close individual panel, you can drag the corner with the arrow of neighboring panel with the same height or width. This is using the outliner to close the properties panel.



The link posted by @poor has this answer, you just have to wait until the end of a 30 second gif to see it in action.  (is there a TL;DW for gifs?)